To provide cellular wireless communication service, a wireless service provider typically operates an access network that functions to connect one or more access terminals (e.g., cell phones, PDAs, laptops, netbooks, tablets, and/or other wirelessly-equipped devices) with one or more transport networks. In a typical access network, an area is divided geographically into a number of coverage areas, such as cells and sectors, each defined by a radio frequency (RF) radiation pattern from a respective base transceiver station (BTS). Within each coverage area, the BTS's RF radiation pattern may provide one or more wireless links, each on a carrier (or set of carriers), over which access terminals may communicate with the access network. In turn, the access network may provide connectivity with the public switched telephone network (PSTN), the Internet, and/or other transport networks.
The wireless links may carry communications between the access network and the access terminals according to any of a variety of wireless protocols. Depending on the protocol employed, each wireless link may also be divided into a plurality of channels for carrying communications between the access network and the access terminals. For example, each wireless link may include a plurality of forward-link channels, such as forward traffic channels, for carrying communications from the access network to the access terminals. As another example, each wireless link may include a plurality of reverse-link channels, such as reverse traffic channels, for carrying communications from the access terminals to the access network.
In many wireless protocols, the access network and active access terminals may engage in a power-control process to control transmission power for communications over established traffic channels. For purposes of illustration, the embodiments herein will be described by way of example with reference to a power-control process carried out by an active access terminal to control the forward transmission power of the access network. It should be understood, however, that a similar power-control process may be carried out by the access network to control the reverse transmission power of the active access terminals.
In an example power-control process, an active access terminal may regularly send power control commands (PCCs) directed to the access network, to control the access network's transmission power on a forward traffic channel to the active access terminal (i.e., the forward transmission power to the active access terminal). For example, the active access terminal may regularly compare a signal-quality metric of forward traffic-channel communications received from the access network to a signal-quality threshold value and thereby decide whether to send a “power up” PCC that instructs the access network to increase its forward transmission power to the active access terminal or a “power down” PCC that instructs the access network to decrease its forward transmission power to the active access terminal. For instance, if the signal-quality metric is less than the signal-quality threshold value (thus indicating a weaker signal), the active access terminal may send a “power up” PCC directed to the access network. Alternatively, if the signal-quality metric is greater than the signal-quality threshold value (thus indicating a stronger signal), the active access terminal may send a “power down” PCC directed to the access network.
As a result of the active access terminal regularly sending PCCs directed to the access network, the access network may regularly receive PCCs from the active access terminal. (It should be understood, however, that the access network may fail to receive some PCCs sent by the active access terminal due to poor reverse-link conditions or other factors.) In response to each PCC received from the active access terminal, the access network may then responsively adjust its forward transmission power to the active access terminal in accordance with the PCC. For instance, in response to receiving a “power up” PCC from the active access terminal, the access network may increase its forward transmission power to the active access terminal. And in response to receiving a “power down” PCC from the active access terminal, the access network may decrease its forward transmission power to the active access terminal.
Advantageously, this power-control process may enable the active access terminal and the access network to balance between keeping traffic-channel communications strong enough to overcome interference and preventing traffic-channel communications from becoming so strong that they unduly interfere with other communications.